Rocky Flats Plant
 

Special Exposure Cohort
 

Petition Evaluation Report
 

Stuart Hinnefeld
 Director
 

National Institute for Occupational Safety and Health
 

Division of Compensation Analysis and Support
 

September 2012
 

Denver, CO
 
 

 

 

 

Petition Overview
 

 August 23, 2011: NIOSH received an 83.13 

petition for period of April 1952 to December 21, 

2005 (for tritium exposures) 

 February 9 2012: Petition qualified for 

evaluation 

 September 5, 2012: Evaluation Report approved
 

 SEC class recommended: None 
 

 

 

 

 

Background
 

 Rocky Flats Plant (RFP) 

•	 Located in Golden, Colorado 

•	 384-acre site, surrounded by ~6000 acre buffer zone 

•	 Approximately 6000 people maximum workforce (~1990) 

•	 Located in Golden, Colorado 

 RFP primarily produced plutonium triggers for, and

recovered plutonium from, nuclear weapons 

•	 SEC00030 evaluation did not adequately address tritium 

•	 Work with some pits and special return material entailed

some tritium potential 
 

 

 

 

 

 

Proposed and Evaluated SEC Class
 

 Petitioner-Proposed class: 

All workers employed at Rocky Flats from April 1, 1952 

to December 31, 2005 

 Class Evaluated by NIOSH: 

All employees of the Department of Energy, its 

predecessor agencies, and their contractors and 

subcontractors with the potential for tritium exposures 

while working at the Rocky Flats Plant in Golden, 

Colorado, during the period from April 1, 1952 to 

December 31, 2005. 
 

 

 

 

 

 

 

 

 

Petition Basis and Concerns
 

 Unmonitored workers 

•	 Petitioner provided information and affidavit statements 

in support of the petitioner’s position that there were 

times when the petitioner was not monitored, specifically 

as it related to tritium. 

•	 NIOSH determined that it has access to personnel or area 

monitoring data for Rocky Flats workers, specifically 

applicable to tritium at the time of the 1973 incident. 

•	 NIOSH determined that a review of tritium records and 

data for all time periods was appropriate, and sufficient to 

support qualifying SEC00192 for further evaluation. 
 

Sources of Available Information
 

 Rocky Flats Plant TBDs (ORAU-TKBS-0011-1 

through ORAU-TKBS-0011-6) 

 NIOSH Site Research Database documents 

 DCAS and ORAUT technical bulletins 

 Case files in NIOSH OCAS Claims Tracking System
 
 

Additional Information Obtained
 

During SEC Petition Evaluation
 

 Interviews with former RFP workers 

 Worker Outreach meetings 

 Classified records reviews 
 

 

 

 

 

 

 

 

 

Previous Dose Reconstructions
 

NIOSH OCAS Claims Tracking System
 

Information available as of January, 2012
 

Totals include claims that are in the earlier SEC classes
 

 RFP claims submitted to NIOSH 1695 

 Dose reconstructions completed, 

or claim otherwise dispositioned, for energy 

employees in the evaluated class 

1605 

 Claims containing internal dosimetry 1442 

 Claims containing tritium bioassay 122 
 

 

 

 

 

Potential Tritium Exposures
 

 Tritium containers 

•	 First two designs (pure fission weapons) phased out circa

1957 

•	 Later design (thermonuclear) had tritium but it was coupled 

at other sites 

 Neutron generators 

•	 Used tritium targets (total inventory in all machines <250 Ci) 

•	 Located in five locations on-site 

 Radiation interactions 

•	 Interactions between transuranics and B, Be, and N can 

produce tritium 
 

 

 

Potential Tritium Exposures—cont.
 

 Contaminated Returns 

•	 The years when contaminated returns could have 

existed in the MED/AEC complex is not certain; it’s 

possible they were not at RFP until late 1960s 

•	 Conservative assumption would be that releases 

from contaminated returns could have occurred at 

any time since RFP plutonium operations commenced 

in 1953 
 

 

 

Source Term for Exposure
 

 Neutron generators and radiation interaction not 

deemed significant 

•	 Tritium (a total of 241 Ci over the operational period 

through 1973) in neutron generator targets spread 

across the site in five different areas 

•	 Estimates of total tritium generated from radiation 

interactions range from 0.2 – 3.2 Ci/yr 

 Contaminated returns deemed a significant 

exposure risk 
 

 

 

 

Source Term for Exposure—cont.
 

 1973 incident involving contaminated return produced 

the highest recorded tritium contamination levels 

 RFP receipt records from 1970-1974 indicated almost 300 

shipments. Four from LLNL were considered likely to 

have been contaminated with tritium 

•	 April 1969 ~60 Ci 

•	 March 1971 ~50 Ci 

•	 December 1971 ~30 Ci 

•	 March 1973 500-2000 Ci 
 

 

 

 

Source Term for Exposure—cont.
 

 In the 1979-1980 time period an evaluation of 

1700 LANL ‘site return’ pits, retrieved from 

stockpile, showed very little tritium (from 0.015 

– 468 mCi/m3) 

 In 1984 radiography of pits (to determine 

structural integrity) was a routine aspect of 

testing, and was sufficient to determine likely 

tritium contamination in a pit received from 

LANL (returned to LANL for disassembly) 
 

 

Incidents
 

 Normal site returns were processed by acid 

dissolution 

 Special returns were ‘hydrided’ and the off-gas 

was burned and filtered before release to the 

atmosphere – this would result in HTO rather 

than elemental tritium 
 

 

 

 

 

 

Incidents—cont.
 

 Special project incident in 1968 released ~600 Ci 

of tritium (no detectable environmental impact 

due to chemical form of tritium – elemental 

tritium release versus tritiated water) 

 1973 incident was a special return, and the offgas was burned resulting in production of HTO 

and the release of 500-2000 Ci 

 1974 incident – tritium release from a 

contaminated shipping container amounted to 

an estimated 1.5 Ci 
 

 

 

Monitoring
 

 Prior to 1973 incident, RFP did not routinely

collect bioassay for tritium (as it was not

anticipated as a component of their mission) 

•	 Handful of tritium samples in SRDB prior to 1973 

(~30) 

•	 Special sampling due to 1973 incident well- documented, 148 workers monitored, 5 deemed to 

have ‘potentially significant exposures’ 

•	 Routine sampling program put in place after 1973 

incident, abandoned for job-specific sampling in 1975 because the results showed zero positive samples 
 

Monitoring—cont.
 

 A review of HP, IH, and EM reports for all years 

indicates limited tritium results 

• Tritium sniffers 

• Triton portable and fixed air monitors 

• Swipe and smear surveys 
 

 

 

Monitoring—cont.
 

 Post-1973, procedures were implemented to 

sample workers working a job involving more 

than 1 mCi tritium 

• One document lists 16 names of personnel to be 

sampled; tritium sampling data for 13 of the 16 

were found in the SRDB 
 

 

 

 

Approach to Dose Reconstruction
 

 Although there were several incidents related to 

tritium at RFP, only the one in 1973 resulted in 

significant personnel exposure. Involved 

personnel were carefully monitored, results are 

numerous, and are available in the SRDB 

 Because of the size and chemical composition of 

this 1973 release (HTO versus elemental tritium) 

NIOSH considers this to be a bounding scenario. 
 

 

 

 

 

Approach to Dose Reconstruction
 

 Rocky Flats started processing the contaminated returns 

in April 1973, not knowing that they were contaminated 

 In June 1973, the state of Colorado detected tritium in 

surrounding surface waters and notified Rocky Flats; 

Rocky Flats maintained that it could not have been the 

source 

 In September 1973, Rocky Flats started investigating and 

found tritium in multiple unexpected locations in the 

workplace 
 

 

 

 

Approach to Dose Reconstruction
 

 Bioassay samples were collected from 148 employees 

who were judged to have been potentially exposed to 

tritium 

 Dose estimates were prepared for employees with the 

highest bioassay results, using “worst case” and “best 

fit” approaches. The “worst case” result of 753 

mrem/year will be adopted as the internal tritium dose 

for all workers from the beginning of Pu operations 

through 1973 to account for potential doses from 

unidentified, but presumably smaller, earlier occurrences 

of contaminated returns 
 

 

 

 

 

 

Approach to Dose Reconstruction
 

 Because of the extent of time over which tritium 

exposures likely occurred (from receipt in April 

until investigation in September), tritium 

exposures from this incident were more chronic 

in nature, rather than single acute exposures. 

This chronic exposure experience is analogous to 

what would have occurred if there were other 

unidentified receipts of contaminated returns 
 

 

 

 

 

 

Evaluation Process
 

 Two-prong test established by EEOICPA and 

incorporated into 42 C.F.R. § 83.13 (c)(1) and 42 

C.F.R. § 83.13 (c)(3): 

1. Is it feasible to estimate the level of radiation doses 

of individual members of the class with sufficient 

accuracy? 

2. Is there a reasonable likelihood that such radiation 

dose may have endangered the health of members of 

the class? 
 

Feasibility of Dose Reconstruction 
 

The process and incident information, along with 

administrative controls and environmental, area, 

and personnel sampling, provide sufficient 

information to estimate doses associated with 

tritium work at the Rocky Flats Plant 
 

 

 

 

Summary
 

Feasibility Findings for Titanium Alloys Manufacturing Petition 

January 1955 – December 1956 

Source of Exposure Reconstruction 

Feasible 

Reconstruction 

NOT Feasible 

Internal X 

- Tritium X 

External N/A